1. Field of the Invention
The present invention relates to a photographic light-sensitive material having an improved resistance to pressure and, more particularly, to a silver halide photographic light-sensitive material which contains tabular silver halide grains having an average aspect ratio of 2 or more, a light-sensitive material containing silver halide grains having a grain surface containing 2 mol % or more of silver iodide, and a color photographic light-sensitive material containing regular crystal grains.
2. Description of the Related Art
Generally, various pressures are applied to a photographic light-sensitive material coated with a silver halide emulsion. For example, a photographic negative film for general purposes is taken up by a patrone, bent when loaded in a camera, or pulled upon winding up of a frame.
On the other hand, a sheet-like film such as a printing light-sensitive material or a direct medical roentgen light-sensitive material is often bent because it is directly handled by human hands.
In addition, all kinds of light-sensitive materials are subjected to a high pressure when cut or processed.
When various pressures are applied to a photographic light-sensitive material as described above, silver halide grains are pressurized via gelatin as a carrier (binder) of the silver halide grains or a plastic film as a support. It is known that photographic properties of a photographic light-sensitive material are changed when a pressure is applied to silver halide grains, as reported in detail in, e.g., K. B. Mather, J. Opt. Soc. Am., 38. 1054 (1984); P. Faelens and P. de Smet. Sci. et. Ind Phot., 25. No. 5. 178 (1954); and P. Faelens. J. Phot. Sci. 2. 105 (1954).
Recently, a strict demand has arisen for a photographic silver halide emulsion, i.e., a demand has arisen for higher levels of toughness such as storage stability and a resistance to pressure in addition to photographic properties such as sensitivity and image quality such as graininess and sharpness. However, it is obvious that pressure marks are enlarged as the sensitivity is increased. Therefore, an emulsion having high sensitivity with less pressure marks is desired. JP-A-63-220228 ("JP-A" means Unexamined Published Japanese Patent Application) discloses tabular grains having improved exposure intensity dependency, storage stability, and a resistance to pressure. However, an improvement in pressure marks caused by scratching in a camera or scratching by a nail is unsatisfactory.
According to the extensive studies made by the present inventors, it is found that fog caused upon application of a pressure to the light-sensitive material is increased if a sensitizing dye is adsorbed on silver halide grains. This phenomenon significantly occurs in tabular grains having large specific surface areas. In order to prevent desorption (especially at a high humidity) of a sensitizing dye from silver halide grains in the light-sensitive material, adsorption of the sensitizing dye is sometimes performed at a high temperature (50.degree. C. or more). However, this operation increases pressure marks, too. In addition, although a method of performing adsorption of a sensitizing dye before chemical sensitization is available as a method of increasing sensitivity, this method also increases pressure marks.
JP-A-2-285346 discloses an improvement in resistance to pressure of a silver halide photographic light-sensitive material containing tabular grains, by hydroquinones. Since, however, the hydroquinones do not have any adsorption group to silver halide grains, they are precipitated on the surface of the light-sensitive material when the material is stored at a high humidity.
To increase the sensitivity and to improve the image quality by the sensitivity increasing technique are central subjects of silver salt photography. Efforts have been made to realize high sensitivity and high image quality by selecting a halogen composition near the grain surface to improve the spectral sensitization sensitivity, by using a thiocyanic acid compound to further improve the spectral sensitization sensitivity, by executing reduction sensitization for silver halide grains to prevent recombination, by using regular crystal grains to obtain a high contrast image, and by combining these techniques. Since, however, each of these techniques has a drawback of enlarging pressure marks, it is difficult to satisfactorily achieve the effects of the techniques in practical applications.